Conventionally, as a technique to trap particulates contained in exhaust gas discharged from a diesel engine, a technique has been known that an engine exhaust emission purifier including a particulate filter is equipped along an exhaust stream of a diesel engine. The particulate filter has a porous honeycomb structure made of ceramics or other material, and the particulate filter has a configuration in which inlets of respective flow paths defined in a lattice form are alternately sealed up while outlets of flow paths whose inlets are unsealed are sealed up, to discharge only exhaust gas that has permeated through porous walls defining the respective flow paths to a down-stream.
Exhaust gas is purified such that particulates in the exhaust gas are trapped inside the porous walls when the exhaust gas permeates through the porous walls. Meanwhile, since the particulates are accumulated inside the porous walls, an increase in exhaust resistance and a rise in differential pressure between the inlet side and outlet side of the particulate filter occur to exert adverse effects on performance of the diesel engine. In view of this, a technique to combust and remove particulates before the particulate filter is brought into such a state is known.
However, there has been a problem in that particulates are not combusted and removed when the load of the diesel engine is low and the temperature of an exhaust gas is low.
Then, a technique is known that particulates accumulated in a particulate filter are removed to recover the particulate trapping capability of the particulate filter, in other words, to regenerate the particulate filter. For example, a technique is known that an electrothermal heater is provided on an upper-stream side of an oxidation catalyst-loaded filter along an exhaust stream of a diesel engine, to raise the temperature of exhaust gas introduced to the oxidation catalyst-loaded filter by heating with the heater (see Patent document 1).    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2001-280121.